- SSc is a disease of unknown origin with the highest incidence occurring in females predominantly after child-bearing years. Recent research has revealed that fetal cells can survive in the maternal circulation for many years. Graft-versus-Host Disease (GVDH) has many similar clinical features to SSc although no evidence for GVHD in SSc has been identified. This investigator has identified by PCR and fluorescence in-situ hybridization (FISH) the presence of Y chromosome nucleated cells in 58% of skin biopsies from active lesions in patients with SSc and 46% of peripheral blood tested of female SSc patients. The investigato hypothesizes that these cells have become activated and have established a GVHD-like response in some female SSc patients. The investigator proposes in the current studies to identify and characterize the fetal cells in frozen and paraffin-embedded section of affected lung, skin, and kidneys in patient with early disease by a combination of magnetic cell sorting, immunophenotyping, and FISH. In addition, she proposes to examine the pattern of cytokine expression of the fetal cells in histologic sections and to isolate, clone, and expand Y chromosome nucleated cells from active lesions. She will also investigate whether expanded lymphocytes from the active lesion can induce Type I collagen mRNA in normal fibroblasts. The studies proposed in this application will identify and functionally characterize the Y chromosome positive cells found in the active lesion of SSc women. Obviously, the aims of this proposal cannot address the pathogenesis of SSc occurring in males, or in woman who have not had recognized pregnancies or male offspring.